• International Journal of Aeronautical and Space Sciences
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• 제8권1호
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• pp.10-20
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• 2007

For spacecraft attitude control, reaction wheel (RW) steering laws with more than three wheels for three-axis attitude control can be derived by using a control allocation (CA) approach.1-2 The CA technique deals with a problem of distributing a given control demand to available sets of actuators.3-4 There are many references for CA with applications to aerospace systems. For spacecraft, the control torque command for three body-fixed reference frames can be constructed by a combination of multiple wheels, usually four-wheel pyramid sets. Multi-wheel configurations can be exploited to satisfy a body-axis control torque requirement while satisfying objectives such as minimum control energy.1-2 In general, the reaction wheel steering laws determine required torque command for each wheel in the form of matrix pseudo-inverse. In general, the attitude control command is generated in the form of a feedback control. The spacecraft body angular rate measured by gyros is used to estimate angular displacement also.⁵ Combination of the body angular rate and attitude parameters such as quaternion and MRPs(Modified Rodrigues Parameters) is typically used in synthesizing the control command which should be produced by RWs.¹ The attitude sensor signals are usually corrupted by noise; gyros tend to contain errors such as drift and random noise. The attitude determination system can estimate such errors, and provide best true signals for feedback control.⁶ Even if the attitude determination system, for instance, sophisticated algorithm such as the EKF(Extended Kalman Filter) algorithm⁶, can eliminate the errors efficiently, it is quite probable that the control command still contains noise sources. The noise and/or other high frequency components in the control command would cause the wheel speed to change in an undesirable manner. The closed-loop system, governed by the feedback control law, is also directly affected by the noise due to imperfect sensor characteristics. The noise components in the sensor signal should be mitigated so that the control command is isolated from the noise effect. This can be done by adding a filter to the sensor output or preventing rapid change in the control command. Dynamic control allocation(DCA), recently studied by Härkegård, is to distribute the control command in the sense of dynamics⁴: the allocation is made over a certain time interval, not a fixed time instant. The dynamic behavior of the control command is taken into account in the course of distributing the control command. Not only the control command requirement, but also variation of the control command over a sampling interval is included in the performance criterion to be optimized. The result is a control command in the form of a finite difference equation over the given time interval.⁴ It results in a filter dynamics by taking the previous control command into account for the synthesis of current control command. Stability of the proposed dynamic control allocation (CA) approach was proved to ensure the control command is bounded at the steady-state. In this study, we extended the results presented in Ref. 4 by adding a two-step dynamic CA term in deriving the control allocation law. Also, the strict equality constraint, between the virtual and actual control inputs, is relaxed in order to construct control command with a smooth profile. The proposed DCA technique is applied to a spacecraft attitude control problem. The sensor noise and/or irregular signals, which are existent in most of spacecraft attitude sensors, can be handled effectively by the proposed approach.

• 한국보건간호학회지
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• 제16권2호
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• pp.271-284
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• 2002

This study was to provide basic materials to help reduce the fatigue by analyzing what effective factor the fatigue of hospital nurses in Gwangju and Jeonnam region. and what causes their fatigue. This descriptive research by Questionaires includes two hospitals in Gwangju. and seven hospitals in Jeonnam region, total 9 hospitals sampled at convenience sampling. The periods of collecting data was from Jul.22, 2002 to Jul. 30, 2002. Multidimensional Fatigue Scale; MFS, developed by Jang Se-Jin(2000) was taken to measure the fatigue. All collected materials were got the statistics by SAS for Windows Release 8.01. The result of this study was as follows. 1. This study included total 740 nurses, whose age ranged from 22 to 50; 30 years old by average. Nurses fatigue mean score was 90.24 (the scope by the measuring instrument is 19-133). Nurses at University Hospitals marked 92.36 and those at General Hospitals marked 87.91 in the mean score of fatigue. 2. They kept tired at work, and felt more tired while working at computer in the hospital. 3. The part of body in which they felt fatigue was the calf and $feet(36.6\%)$, the shoulders and back of the $neck(30.7\%)$, and the whole $body(10.8\%)$ and the reason that they felt tired at work was mental $stress(33.0\%)$, overworking(25.2\%)$, and irregular working $conditions(14.7\%)$ in order. 4. The solution to their fatigue at work appeared nothing by $50.1\%$, and the way of releasing fatigue after work indicated getting some $sleep(30.8\%)$, and taking a bath or a $shower(21.7\%)$ in order. 5. The degree of fatigue depending on whether they were satisfied with their pay and labor condition appeared low: and when they were satisfied with doctors. and when they were getting on well with caregivers. 6. The effective factor of the degree of fatigue appeared: the influence that fatigue in the hospital makes on daily life was $10.6\%$, the cause of fatigue at work, $9.3\%$, time of fatigue at work, $7.8\%$, the relationship with caregivers, $5.3\%$. and these explanatory$(R^2)$ variables.$33\%$. To conclude. the degree of nurses' fatigue appeared high. and it was higher in nurses at University Hospitals than in ones at General Hospitals. In addition, the influence that fatigue from the hospitals made on daily life was the most explanatory.

• 해양환경안전학회지
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• 제13권1호
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• pp.1-7
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• 2007

동해의 해양 심층수 자원 기반 환경 연구의 일부로 청결기술을 적용하여 해수 중의 용존 미량금속(Cd, Co, Cu, Ni, Pb, Zn) 농도 분포와 변화를 조사하였다. 강원과 경북 지역에 총 6개 정점을 선정하고, 각 지역마다 최대 채수 수심 각각 200-300m와 500m까지 시료를 채취하였다. 본 연구의 미량금속을 위한 연안해수 표준물질(CASS-4)의 분석 결과 각 원소 평균 회수율은 Co의 89.4%에서 Cd의 99.8%의 범위였다. 용존 미량원소의 분포는 해역 및 시기적인 변화가 다양하게 나타났다. Cd, Ni, Zn의 경우는 영양염 의존형으로 표층에서 낮고 저층으로 갈수록 증가하는 경향이 뚜렷하였다. 그러나 Co, Cu, Pb은 수직적으로 불규칙적인 분포를 나타내었다. 본 연구의 동해 심층수 원수의 중금속 농도는 해역별 수질 기준과 먹는 물 기준을 만족하였다.

• 여성건강간호학회지
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• 제9권2호
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• pp.105-112
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• 2003

The survey was conducted to look out the characteristics of menstruation and it's management, menstrual attitudes and degree of dysmenorrhea in the adult women. The subjects were 601 women, aged 20 year old and over, selected by convenient sampling. The results were as follows; 1. The mean age of the subjects was 29.1 years, the subjects were consisted of 346 unmarried and 304 delivery experienced person. 2. The characteristics of menstruation were as follows ; irregular 167 person(27.8%), painful 451 person(75%), mean score of pain was 5.9 point and first day was most severe(45.1%). On the while, they have used the method to manage the pain such as "endure 50.8%", "to have a medicine 31.5%". 3. Menstrual attitudes were as follows; attitudes was negative such as it was meaningful as a woman (78.9%), only for birth a baby (51.6%), and menstruation was acceptable (42.9%), hope to get away(28.8%). 4. The degree of dysmenorrhea was a significant difference by age(F=4.0, P<0.01). Especially, in the subcategory, it was significant except for water retension. That is, lower concent ration(F=2.60, p<0.05), negative affect(F=3.09, p<0.05), behavior change(F=6.41, p<0.050), pain(F=3.89, p<0.01), autonomic nerve response(F=2.80, p<0.05). We can conclude there were many women to have negative attitudes to menstruation and first day was most severe dysmenorrhea and it was different by age. From this results, we may suggest as follows; 1. We suggest the program for women to have a positive attitudes will be developed. 2. We can suggest that we need to develop the active and effective method to control dysmenorrhea in the first day during menstruation.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2003년도 춘계학술대회 논문집
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• pp.214-214
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• 2003

During a model test of Hutton TLP, a "ringing" response was first observed about 20 years ago. This phenomenon is a resonant build up over the time of wave period and this burst-like motion can cause the extreme load on the TLP tether. It is often detected in the large and steep irregular waves but the generation mechanism leading to the "ringing" is not yet well understood. According to the research since then, the higher order harmonic components may account for the "ringing" on the floating offshore structures. The main purpose of the present research is, thus, to measure the higher harmonic forces exerted on a vertical truncated circular column and to compare them with available data. A vertical truncated cylinder with a diameter of 3.5inch and a draft of 10.5inch is used as a test structure, which is a scaled model of ISSC TLP column. The cylinder is installed at a distance of 45ft from the wave maker in order to avoid parasitic waves created in the wave flap. Attached to the upper part of the cylinder are two force gages to measure the horizontal (surge) and vertical (heave) forces on the cylinder. The incoming waves are Stokes waves with a slope ranging from 0.06 to 0.24. The forces and waves are measured for 60 seconds with a sampling rate of 50 Hz. Among the recorded data, the first 10 waves are excluded because of transient behavior of the waves and the next The horizontal and vertical forces are analyzed up to 5th order harmonics. The horizontal forces are then compared to the values from the theoretical model called "FNV model". In addition, force transfer functions are also investigated. Major findings in this research are below. 1) The first order forces measured are slightly larger than the theoretical values of "FNV model" 2) The "FNV model" considerably overpredicts the second order forces. 3) The larger the amplitude and more extreme the wave slope, the smaller the predictions are compared to the experimental. 4) The higher harmonic forces are significantly smaller than the first harmonic force for all wave parameters. 5) The normalized forces vs. waves slopes are almost constant in the lower harmonics but vary a lot in the higher harmonics. 6) The trend of forces is more nonlinear in the horizontal forces than in the vertical forces as the wave slope increases. 7) The part of the results above is also observed by other researchers and confirmed again through the present work.

• 한국해양학회지:바다
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• 제24권3호
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• pp.400-421
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• 2019

본 연구는 남해안의 대표 만 중에 하나인 광양만에서 저서생태계 특성 파악을 목적으로 중형저서동물 군집의 계절적 분포 특성을 조사하였다. 2010 ~ 2011년까지 20개 정점에서 계절별로 총 8회 조사를 실시하였으며, 연구기간 동안 출현한 중형저서동물 분류군 중 선충류와 저서성 요각류가 가장 우점하는 분류군으로 나타났다. 2011년 여름에 만 내측 정점 10에서 가장 낮은 서식밀도를 나타냈으며($13ind.10m^{-2}$), 2011년 겨울에 만 내측 정점 4에서 가장 높은 서식밀도를 나타냈다($3,109ind.10m^{-2}$). 서식밀도의 계절적 변동 경향은 뚜렷하게 나타나지 않았으나, 중형저서동물의 군집 조성은 계절별로 환경요인에 더욱 영향을 받는 것으로 나타났다. 특히 우점 분류군인 저서성 요각류의 서식밀도는 여름철 퇴적물 내 유기물 함량 및 평균 입도와 음의상관관계가 나타났으나(p<0.05, p<0.01), 선충류의 서식밀도는 겨울철 평균 입도와 저층 수온을 제외하고 환경요인과 유의한 상관관계가 나타나지 않았다. 중형저서동물의 일반적인 서식밀도 변동 경향은 겨울철 낮은 수온에 의해 낮은 서식밀도를 나타내다 수온이 높아지는 봄철과 여름철에 증가하고 가을에 감소하는 경향과는 다르게 광양만은 일정한 경향 없이 불규칙한 변동을 나타냈다. 이러한 계절적 변동 경향으로 미루어 광양만의 저서생태계는 자연적인 환경요인 보다는 인위적 환경요인에 의해 영향을 받고 있음을 시사할 수 있다.

• 한국산학기술학회논문지
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• 제22권6호
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• pp.321-331
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• 2021

본 연구는 성인 1인 가구의 고위험 음주에 관한 영향요인을 분석하고자 시도되었다. 본 연구는 2018년 지역사회 건강조사 자료를 활용하였으며, 연구대상자는 만 19세 이상의 음주경험이 있는 1인 가구 32,389명이었다. 자료 분석을 위해 대상자를 지역사회건강조사의 고위험 음주율 지표에 따라 고위험음주군을 추출하여 인구사회학적 특성, 건강관련 특성의 차이 및 고위험음주 영향요인을 파악하였다. 자료 분석은 IBM SPSS 25.0 프로그램을 이용하여 복합표본설계를 적용하였다. 연구결과, 우리나라 1인 성인 가구의 고위험 음주율은 15.0%(남성 25.8%, 여성 5.8%)로 나타났고, 고위험 음주의 영향요인은 연령과 고등학교 이하의 교육수준, 서비스직 종사, 흡연을 하는 경우, 우울감을 경험한 경우, 고혈압을 진단받은 경우, 아침식사를 규칙적으로 하지 않는 경우가 남성과 여성의 공통요인으로 나타났으며, 남성에게만 영향을 주는 요인은 스트레스, 여성에게만 영향을 주는 요인은 당뇨 진단을 받은 경우로 나타났다. 연령의 경우 남성은 장년층에서, 여성은 20-30대 청년층에서 고위험 음주 위험성이 높은 것으로 나타났다. 국가 경제력의 원동력인 청장년층의 고위험 음주율이 높고, 특히 스트레스나 우울감 경험 등의 정신적인 요인이 고위험 음주 영향요인으로 나타난 본 연구결과는 1인 가구의 고위험 음주율을 낮추기 위해서는 건강행태 및 생활습관의 세밀한 분석을 통한 맞춤형 보건정책과 함께 정신건강 프로그램의 연계가 필요함을 시사한다.

• 지구물리와물리탐사
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• 제25권3호
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• pp.140-161
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• 2022

탄성파 탐사 자료 획득 시 자료의 일부가 손실되는 문제가 발생할 수 있으며 이를 위해 자료 보간이 필수적으로 수행된다. 최근 기계학습 기반 탄성파 자료 보간법 연구가 활발히 진행되고 있으며, 특히 영상처리 분야에서 이미지 초해상화에 활용되고 있는 CNN (Convolutional Neural Network) 기반 알고리즘과 GAN (Generative Adversarial Network) 기반 알고리즘이 탄성파 탐사 자료 보간법으로도 활용되고 있다. 본 연구에서는 손실된 탄성파 탐사 자료를 높은 정확도로 복구하는 보간법을 찾기 위해 CNN 기반 알고리즘인 U-Net과 GAN 기반 알고리즘인 cWGAN (conditional Wasserstein Generative Adversarial Network)을 탄성파 탐사 자료 보간 모델로 사용하여 성능 평가 및 결과 비교를 진행하였다. 이때 예측 과정을 Case I과 Case II로 나누어 모델 학습 및 성능 평가를 진행하였다. Case I에서는 규칙적으로 50% 트레이스가 손실된 자료만을 사용하여 모델을 학습하였고, 생성된 모델을 규칙/불규칙 및 샘플링 비율의 조합으로 구성된 총 6가지 테스트 자료 세트에 적용하여 모델 성능을 평가하였다. Case II에서는 6가지 테스트 자료와 동일한 형식으로 샘플링된 자료를 이용하여 해당 자료별 모델을 생성하였고, 이를 Case I과 동일한 테스트 자료 세트에 적용하여 결과를 비교하였다. 결과적으로 cWGAN이 U-Net에 비해 높은 정확도의 예측 성능을 보였으며, 정량적 평가지수인 PSNR과 SSIM에서도 cWGAN이 높은 값이 나타나는 것을 확인하였다. 하지만 cWGAN의 경우 예측 결과에서 추가적인 잡음이 생성되었으며, 잡음을 제거하고 정확도를 개선하기 위해 앙상블 작업을 수행하였다. Case II에서 생성된 cWGAN 모델들을 이용하여 앙상블을 수행한 결과, 성공적으로 잡음이 제거되었으며 PSNR과 SSIM 또한 기존의 개별 모델 보다 향상된 결과를 나타내었다.

• 한국지리정보학회지
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• 제22권3호
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• pp.10-20
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• 2019

전 세계적으로 기후변화로 인한 불규칙적인 강우의 영향으로 수계에서는 비점오염에 의한 부영양화, 녹조현상 등이 빈번하게 발생되고 있다. 특히 이러한 수계오염은 원활한 용수공급을 위한 저수지 유속이 느린 하천이 인접해있고, 축사 퇴비 등이 다수 분포해 있어 비점오염의 수계유입이 쉬운 농업지역이 취약하다. 따라서, 본 연구에서는 UAV(Unmanned Aerial Vehicle) 영상과 수계부영양화를 발생시키는 총인 총질소, 녹조발생과 간접적인 연관성이 있는 클로로필-a의 상관분석을 통해 소하천 수질 특성 파악에 UAV의 활용 가능성을 분석하였다. 분석에는 대상지인 양천, 함양위천 소권역에서 수집한 다중분광 영상 및 녹조탐지에 사용되는 식생지수 NDVI(Normalized difference vegetation index), NDRE(Normalized Difference Red edge), CIRE(Chlorophyll Index Red edge)를 활용하였다. 채수지점에 대한 영상값과 수질분석 값의 상관관계를 분석한 결과 총인은 유의수준 0.05 이내에서 CIRE(0.66)와 클로로필-a는 Blue(-0.67), Green(-0.66), NDVI(0.75), NDRE(0.67), CIRE(0.74)와 상관관계를 보였다. 총질소는 유의수준 0.05에서 Red(-0.64), Red edge(-0.64), NIR(-0.72)와 상관관계를 보였다. 본 연구결과를 통해 UAV 기반 다중분광 영상과 수질오염 발생 인자에 대한 유의미한 상관관계를 확인하였고, 녹조탐지에 사용하는 식생지수의 경우 클로로필-a뿐만 아니라 총인의 파악에도 활용할 수 있는 가능성을 확인하였다. 이는 농업지역의 비점오염 관리우심 지역 선정 등 관리대책을 마련하는데 유의미한 자료로 사용될 수 있을 것으로 판단된다.

• 대한간호학회지
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• 제12권2호
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• pp.1-26
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• 1982

The main purpose of this study was to test the effect of the structured information on the sleep amount of the patients undergoing open heart surgery. This study has specifically addressed to the Following two basic research questions: (1) Would the structed in formation influence in the reduction of sleep disturbance related to anxiety and Physical stress before and after the operation? and (2) that would be the effects of the structured information on the level of preoperative state anxiety, the hormonal change, and the degree of behavioral change in the patients undergoing an open heart surgery? A Quasi-experimental research was designed to answer these questions with one experimental group and one control group. Subjects in both groups were matched as closely as possible to avoid the effect of the differences inherent to the group characteristics, Baseline data were also. collected on both groups for 7 days prior to the experiment and found that subjects in both groups had comparable sleep patterns, trait anxiety, hormonal levels and behavioral level. A structured information as an experimental input was given to the subjects in the experimental group only. Data were collected and compared between the experimental group and the control group on the sleep amount of the consecutive pre and post operative days, on preoperative state anxiety level, and on hormonal and behavioral changes. To test the effectiveness of the structured information, two main hypotheses and three sub-hypotheses were formulated as follows; Main hypothesis 1: Experimental group which received structured information will have more sleep amount than control group without structured information in the night before the open heart surgery. Main hypothesis 2: Experimental group with structured information will have more sleep, amount than control group without structured information during the week following the open heart surgery Sub-hypothesis 1: Experimental group with structured information will be lower in the level of State anxiety than control group without structured information in the night before the open heart surgery. Sub-hypothesis 2 : Experimental group with structured information will have lower hormonal level than control group without stuctured information on the 5th day after the open heart surgery Sub-hypothesis 3: Experimental group with structured information will be lower in the behavioral change level than control group without structured information during the week after the open heart surgery. The research was conducted in a national university hospital in Seoul, Korea. The 53 Subjects who participated in the study were systematically divided into experimental group and control group which was decided by random sampling method. Among 53 subjects, 26 were placed in the experimental group and 27 in the control group. Instruments; (1) Structed information: Structured information as an independent variable was constructed by the researcher on the basis of Roy's adaptation model consisting of physiologic needs, self-concept, role function and interdependence needs as related to the sleep and of operational procedures. (2) Sleep amount measure: Sleep amount as main dependent variable was measured by trained nurses through observation on the basis of the established criteria, such as closed or open eyes, regular or irregular respiration, body movement, posture, responses to the light and question, facial expressions and self report after sleep. (3) State anxiety measure: State Anxiety as a sub-dependent variable was measured by Spi-elberger's STAI Anxiety scale, (4) Hormornal change measure: Hormone as a sub-dependent variable was measured by the cortisol level in plasma. (5) Behavior change measure: Behavior as a sub-dependent variable was measured by the Behavior and Mood Rating Scale by Wyatt. The data were collected over a period of four months, from June to October 1981, after the pretest period of two months. For the analysis of the data and test for the hypotheses, the t-test with mean differences and analysis of covariance was used. The result of the test for instruments show as follows: (1) STAI measurement for trait and state anxiety as analyzed by Cronbachs alpha coefficient analysis for item analysis and reliability showed the reliability level at r= .90 r= .91 respectively. (2) Behavior and Mood Rating Scale measurement was analyzed by means of Principal Component Analysis technique. Seven factors retained were anger, anxiety, hyperactivity, depression, bizarre behavior, suspicious behavior and emotional withdrawal. Cumulative percentage of each factor was 71.3%. The result of the test for hypotheses show as follows; (1) Main hypothesis, was not supported. The experimental group has 282 minutes of sleep as compared to the 255 minutes of sleep by the control group. Thus the sleep amount was higher in experimental group than in control group, however, the difference was not statistically significant at .05 level. (2) Main hypothesis 2 was not supported. The mean sleep amount of the experimental group and control group were 297 minutes and 278 minutes respectively Therefore, the experimental group had more sleep amount as compared to the control group, however, the difference was not statistically significant at .05 level. Thus, the main hypothesis 2 was not supported. (3) Sub-hypothesis 1 was not supported. The mean state anxiety of the experimental group and control group were 42.3, 43.9 in scores. Thus, the experimental group had slightly lower state anxiety level than control group, howe-ver, the difference was not statistically significant at .05 level. (4) Sub-hypothesis 2 was not supported. . The mean hormonal level of the experimental group and control group were 338 ㎍ and 440 ㎍ respectively. Thus, the experimental group showed decreased hormonal level than the control group, however, the difference was not statistically significant at .05 level. (5) Sub-hypothesis 3 was supported. The mean behavioral level of the experimental group and control group were 29.60 and 32.00 respectively in score. Thus, the experimental group showed lower behavioral change level than the control group. The difference was statistically significant at .05 level. In summary, the structured information did not influence the sleep amount, state anxiety or hormonal level of the subjects undergoing an open heart surgery at a statistically significant level, however, it showed a definite trends in their relationships, not least to mention its significant effect shown on behavioral change level. It can further be speculated that a great degree of individual differences in the variables such as sleep amount, state anxiety and fluctuation in hormonal level may partly be responsible for the statistical insensitivity to the experimentation.